Frequency synthesizer



May 3, 1966 H. A. ROBINSON FREQUENCY SYNTHESIZER 2 Sheets-Sheet 1 FiledMarch 31, 1964 zmo EEC n Y. E1553: m m vm E 2 oi m mm NI"- N\ mm 1 V 5Tw INVENTOR. HARRIS ALEXANDER ROBINSON MMM ATTORNEY y 3, 1966 H. A.ROBINSON 3,249,887

FREQUENCY SYNTHESIZER Filed March 51, 1964 2 Sheets-Sheet 2 E l (D IINVENTOR. HARRIS ALEXANDER ROBINSON ATTORNEY United States Patent3,249,887 FREQUENCY SYNTHESIZER Harris Alexander Robinson, Palmyra,N.J., assignor, by mesne assignments, to the United States of America asrepresented by the Secretary of the Navy Filed Mar. 31, 1964, Ser. No.356,340 1 Claim. (Cl. 33138) The present invention relates to novel andimproved frequency synthesizing apparatus and more particularly toapparatus for developing a large number of electrical oscillatorysignals at predetermined decimal interval frequencies from a single highstability reference frequency source.

In various electronic applications, use of a signal generator thatprovides a plurality of signals at predetermined discreet frequenciesoften becomes highly desirable. Although various types of such multiplefrequency signal generators have been devised in the past, considerabledifficulty has been experienced heretofore in designing a frequencysynthesizer which is relatively simple in construction and yet highlyreliable and convenient in use.

It is therefore a principal object of the present invention to provide anovel and improved frequency synthesizer which includes no elaboratefilters, phase locked loops, movable tuning slugs or switched orvariable capacitors.

It is a further object of the present invention to provide a novel andimproved frequency synthesizer having a high order of commonality ofidentical and interchangeable mixers, filters, multipliers, dividers andother component modules.

It is a further object of the present invention to provide a novel andimproved frequency synthesizer which is capable of producing up tothirty thousand signals having unique frequencies at one kilocycledecimal intervals from a single high stability reference frequencysource.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

FIGS. lA and 1-B when placed side by side illustrate a preferredembodiment of the present invention.

Referring now to the drawing, the conventional reference frequencyoscillator 3 generates a 2 me. signal which is successively doubled inthe factor of two fre quency multiplier circuits M1, M-2, M3 and M-4 toprovide a 32 mc. frequency signal on conductor 5. The 4 mo. signal atthe output of frequency multiplier M1 is coupled to the mixer circuit X1through conductor 7. The 2 mc. signal from the standard referenceoscillator 3 is also coupled to mixer X-1 through conductor 9, thefactor of five frequency divider D-1 and conductors 11 and 13. Theoutput circuit of mixer X-1 is coupledto the spectrum generator 15through conductor 17, amplifier 19, and conductor 21. The output circuitof frequency divider D1 is also coupled to the spectrum generator 15through conductor 11, the factor of four frequency divider D2 andconductor 23. The output circuit of spectrum generator 15 is connectedto the 4.1 mc. signal line 41, the 4.2 mc. signal line 42, the 4.3 mc.signal line 43, the 4.4 -mc. signal line 44, the 4.5 mc. signal line 45,the 4.6 mc. signal line 46, the 4.7 mc. signal line 47, the 4.8 mc.signal line 48, and the 4.9 mc. signal line 49 through amplifier 50 andrespectively through crystal filters F1 through F-9 and amplifiers 51through 59.

The 2 mc. signal from the standard oscillator 3 is coupled to the mixerX-Z through conductor 25. The 32 mc. signal on conductor is'also coupledto the mixer X-2 through conductor 27. The output circuit of mixer X-2is coupled to mixer X3 through conductor 29. The 4.9 mc. line 49 is alsoconnected to mixer X-3 through 3,249,887 Patented May 3, 1966 conductor31. The 34.9 mc. signal, derived in a manner which will be more apparenthereinafter, in the output circuit of mixer X-3 energizes conductor 33.

The 32 mc. line 5 is connected to mixer X-4 through conductor 35. The4.9 mc. line 31 is also connected to mixer X-4. The 36.9 mc. signal,derived in a manner which will be more apparent hereinafter, in theoutput circuit of mixer X-4 energizes conductor 37.

The 32 mc. line 5 is connected to mixer X5 through conductor 38. Theoutput circuit of frequency multiplier M2 is also coupled to mixer X5through conductor 39. The output circuit of mixer X-5 is coupled tomixer X-6 through conductor 36. The 4.1 mc. line 41 is also coupled tomixer X-6 through conductor 34. The 35.9 mc. signal, derived in a mannerwhich will be more apparent hereinafter, in the output circuit of mixerX-6 energizes conductor 32.

Referring nowparticularly to FIG. l-B of the drawing, it will be notedthat the ten contacts a-j on the stator of selector switch 61 arerespectively connected to signal lines 40-49 through resistors R-1R-10.The base of the rotor of switch 61 is preferably generally disk-shapedand is constructed of a suitable electrically non-conductive material.The centrally located electrically conductive arm 63 mounted on rotorextends outwardly radially and selectively engages contacts u-j on thestator. The sectored electrically conductive annulus 65 secured to theperipheral edge of the rotor is connected to ground through conductor 67and engages each of the nonselected contacts on the stator. The variablearm 63 of switch 61 is connected to mixer X-7 through conductor 69. The32 mc. line 5 and the 4 mc. line 40 are each connected to input circuitsof the mixer X8. The output circuit of mixer X-8 is coupled to mixer X-7through bandpass filter F-10. Y

The output circuit of mixer X-7 is coupled to mixer X-9 through thebandpass filter F-ll, the factor of ten frequency divider D3 andconductor 70. Mixer X9, which is also energized by the 32 me. signal onconductor 5, is coupled to mixer X10 through bandpass filter F-12.Selector switch 71 is similar to switch 61 described hereinabove andincludes the variable arm 73, ten stator contacts a-j which arerespectively connected to lines 40-49 through resistors R-ll-R-20, andthe grounded sectored annulus 75. The variable arm 73 of switch 71 isconnected to mixer X10 through conductor 79.

The output circuit of mixer X-10 is coupled to mixer X-ll throughbandpass filter F-13, the factor of ten frequency divider D-4 andconductor 80. Mixer X11, which is also energized by the 32 me. signal onconductor 5, is coupled to mixer X-12 through bandpass filter F-14.Selector switch 81 is similar to switch 61 described hereinabove andincludes the variable arm 83, ten stator contacts a which arerespectively connected to lines 40-49 through resistors R21R-30, and thegrounded sectored annulus 85. The variable arm 83 of switch 81 isconnected to mixer X-12 through conductor 89.

The output circuit of mixer X-12 is coupled to mixer X-13 through thebandpass filter F-15, the factor of ten frequency divider D-5 andconductor 90. Mixer X- 13, which is also energized by the 32 mo. signalon conductor 5, is coupled to mixer X-14 through bandpass filter F-16.Selector switch 91 is similar to switch 61 described above and includesthe variable arm 93, ten stator contacts a-j which are respectivelyconnected to lines 40-49 through resistors R31R-40, and the groundedsectored annulus 95. The variable arm 93 of switch 91 is connected tomixer X-14 through conductor The output circuit of mixer X-14 is coupledto mixer X-15 through bandpass filter F-17. Selector switch 101 includesthe variable arm 103, three stator contacts a, b and c which arerespectively connected to lines 32, 33 and 37 through resistors R-41,R-42 and R-43 and the grounded sectored annulus 105. The variable arm103 of switch 101 is connected to mixer X-15 through conductor 109. Theoutput circuit of mixer X-15 is coupled to the output conductor 111 ofthe frequency synthesizer of the present invention through filter F18,the factor of five frequency multiplier M- and the factor of twofrequency multiplier M-6.

Inasmuch as the specific design of the above described mixers, filters,frequency multipliers and dividers, and the spectrum generator may takeany suitable conventional form and of themselves form no part of thepresent invention, a detailed description of the same is not providedherein for the sake of simplicity. For a complete understanding of theinvention, it need only be understood that each of the similarlydesigned mixers X1X 15 combine their input signals in a circuit having anonlinear impedance such that upper and lower sideband frequency signalsare developed, that the various fibers F1F18 are designed to pass aparticular sideband or other desired frequency, that the frequencydividers D1D5 and the frequency multipliers M1M6 lock on the desiredmultiples or submultiples of the input signal, and that the spectrumgenerator 15 is overmodulated to provide a plurality rather than a pairof sideband frequencies on either side of the 4.4 mc. input signal.

In operation, the frequency of the basic reference 2 mo. signalgenerated by oscillator 3 is doubled in the frequency multiplier M1 toprovide a 4 mc. signal on conductor 40. The frequency of the 4 mc.signal is then doubled again in frequency multiplier M-2 to provide a 8me. signal on conductor 39. The frequency of the 8 mc. signal is thendoubled and redoubled in frequency multipliers M-3 and M-4 to provide a32 me. signal on conductor 5.

The frequency of the 2 mc. signal on conductor 9 is also subdivided by afactor of five in frequency divider D-l to provide a .4 mc. signal onconductor 11. The frequency of the .4 mc. signal is then subdivided by afactor of four in frequency divider D-2 to provide a .1 mo. signal onconductor 23, which energizes the spectrum generator 15. The 4 mc.signal on conductor 7 and the .4 mc. signal on conductor 13 are thencombined in the non-linear circuit of mixer X-l to provide a 4.4 mc.sideband signal on conductor 17 which is passed through amplifier 19 tospectrum generator 15. The 4.4 mc. signal and the .1 mc. signal onconductor 23 are combined in the overmodulated generator 15 to provide4.1 mc., 4.2 mc., 4.3 mc., 4.4 mc., 4.5 mc., 4.6 mc., 4.7 mc., 4.8 me.and 4.9 mc. signals which are amplified in amplifier 50 and respectivelypassed through filters F1F9 and amplifiers 51-59 to conductors 41-49.

The 2 mc. signal from reference oscillator 3 on conductor 25 is alsocombined with the 32 me. signal on conductor 27 in the non-linearcircuit of mixer X-2 to provide a 30 mc. sideband signal on conductor29. The 30 mc. signal and the 4.9 mc. signal on conductor 31 are thencombined in the non-linear circuit of mixer X-3 to provide a 34.9 mc.sideband signal on conductor 33.

The 8 mc. signal on conductor39 is combined in the non-linear circuit ofmixer X-5 with the 32 me. signal on conductor 35 to provide a mc'.sideband signal on conductor 36. The 40 mc. signal and the 4.1 mc.signal on conductor 34 are then combined in the non-linear circuit ofmixer X6 to provide the 35.9 mc. sideband signal on conductor 32.

The 32 mc. Signal on conductor 35 is combined in the non-linear circuitof mixer X-14 with the 4.9 mc. signal on conductor 31 to provide the36.9 mc. sideband signal on conductor 37.

The 32 mc. signal on conductor 5 is'then combined in the non-linearcircuit of mixer X8 with the 4 mc. signal on conductor 40 to provide a36 me. sideband signal which is fed through the 36 mc. to 36.1 mc.bandpass filter 1 -10 to mixer X7. The variable arm 63 of switch 61 isthen set to combine a selected signal on conductors 40-49 with the 36me. signal from filter F-10 in the nonlinear circuit of mixer X-7 toprovide any of the ten kc. separated sideband signals between 40 mc. and40.9 mc. This band of ten signals is then passed through the 40 mc. to41 mc. bandpass filter F-11 to frequency divider D3 where the frequencyof each signal is subdivided by a factor of ten.

Any of the resulting ten 10 kc. separated signals between 4 mc. and 4.09me. are then combined in the nonlinear circuit of mixer X9 with the 32mc. signal on conductor 5 to provide ten 10 kc. separated signalsbetween 36 mc. and 36.09 mc. which are fed through the 36 mc. to 36.1mc. bandpass filter F-12 to mixer X-10. The variable arm 73 of switch 71is then set to combine a selected signal on conductors 40-49 with any ofthe ten signals between 36 mc. and 36.09 mc. from filter F12 in thenon-linear circuit of mixer X-10 to provide any of the one hundred 10kc. separated sideband signals between 40 mc. and 40.99 mc. This band ofone hundred signals is then passed through the 40 me. to 41 mc. bandpassfilter F-13 to frequency divider D-4 where the frequency of each signalis subdivided by a factor of ten.

Any of the resulting one hundred 1 kc. separated signals between 4 mc.and 4.099 mc. are then combined in the non-linear circuit of mixer X11with the 32 me. signal on conductor 5 to provide one hundred 1 kc.separated signals between 36 me. and 36.099 mc., which are fed throughthe 36 mc. to 36.1 mc. bandpass filter F-14 to mixer X-IZ. The variablearm 83 of switch 81 is then set to combine a selected signal onconductors 40-49 with any of the one hundred signals between 36 mc. and36.099 me. from filter F14 in the non-linear circuit of mixer X-12 toprovide any of the one thousand 1 kc. separated sideband signals between40 mc. and 40.999 mc. This band of one thousand signals is then passedthrough the 40 me. to 40.1 mc. bandpass filter F-15 to frequency dividerD-S where the frequency of each signal is subdivided by a factor of ten.

Any of the resulting one thousand .1 kc. separated signals between 4 me.and 4.0999 me. are then combined in the non-linear circuit of mixer X-13with the 32 me. signal on conductor 5 to provide one thousand .1 kc.separated signals between 36 me. and 36.0999 mc., which are fed throughthe 36 me. to 36.1 mc. bandpass filter 5-16 to mixer X-14. The variablearm 93 of switch 91 is then set to combine a selected signal onconductors 40-49 with any of the one thousand signals between 36 mc. and36.0999 mc. from filter F16 in the non-linear circuit of mixer X-14 toprovide any of ten thousand .1 kc. separated sideband signals between 40mc. and 40.9999 mc.

This band of ten thousand signals is then passed through the 40 mc. to41 mc. bandpass filter F-17 to the mixer X-15. The variable arm 103 ofswitch 101 is then set to combine a selected signal on conductor 32, 33or 37 with any of the ten thousand signals between 40 mc. and 40.9999mc. from filter F-17 in the non-linear circuit of mixer X-15 to provideany of the thirty thousand .1 kc. separated difference sideband signalsbetween 3.1 mc. and 6.1 me. This band of thirty thousand signals is thenpassed through the 3.1 mc. to 6.1 mc. bandpass filter F-18 and throughfrequency multipliers M-5 and M6 which increase the frequency of eachsignal by a factor of ten to provide the desired thirty thousand 1 kc.separated sig- What is claimed is:

An electronic frequency synthesizer comprising:

(a) a reference oscillator which generates a 2 megacycle signal;

(b) means coupled to the reference oscillator for generating a 4megacycle signal;

(c) means coupled to the reference oscillator for generating a 32megacycle signal;

(d) a spectrum generator which is coupled to the reference oscillatorand which provides nine 100 kilocycle separated signals between 4.1megacycles and 4.9 megacycles;

(e) means coupled to the reference oscillator for generating 34.9megacycle, 35.9 megacycle and 36.9 megacycle signals;

(f) means for combining the 4 megacycle and the 32 megacycle signals andfiltering the resulting output signals to obtain a 36 megacycle signal;

(g) means for combining the 36 megacycle signal with any of the signalsbetween 4 megacycles and filtering the resulting output signals and 4.9megacycles to obtain ten 100 kilocycle separated signals between 40megacycles and 40.9 megacycles; v

(h) means for subdividing the frequency of the signals between 40megacycles and 40.9 megacycles by a factor of ten to obtain tenkilocycle separated signals between 4 megacycles and 4.09 megacycles;

(i) means for combining the ten signals between 4 megacycles and 4.9megacycles with the 32 megacycle signal and filtering the resultingoutput signals to obtain ten 10 kilocycle separated signals between 36megacycles and 36.09 megacycles;

(j) means for combining the signals between 36 megacycles and 36.09megacycles with any of the signals between 4 megacycles and 4.9megacycles and filter ing the resulting output signals to obtain onehundred l0 kilocycle signals between 40 megacycles and 40.99 megacycles;

(k) means for subdividing the frequency of the signals between 40megacycles and 40.99 megacycles by a factor of ten to obtain one hundredone kilocycle separated signals between 4 megacycles and 4.099megacycles; Y

(1) means for combining the hundred signals between 4 megacycles and4.099 megacycles with the 32 megacycle signal and filtering theresulting output signals to obtain one hundred one kilocycle separatedsignals between 36 megacycles and 36.099 megacycles;

(m) means for combining the hundred signals between 36 megacycles and36.099 megacycles with any of the signals between 4 megacycles and 4.9megacycles and filtering the resulting output signals to obtain onethousand one kilocycle separated signals between 40 mega-cycles and40.999 megacycles;

(11) means for subdividing the frequency of the signals between 40megacycles and 40.999 megacycles by a factor of ten to obtain onethousand one hundred cycle separated signals between 4 megacycles and4.0999 megacycles;

(0) means for combining the thousand signals between 4 mega-cycles and4.0999 megacycles with the 32 megacycle signal and filtering theresulting output -signals to obtain one thousand one hundred cycleseparated signals between 36 megacycles and 36.0999 megacycles;

(p) means for combining the signals between 36 megacycles and 36.0999megacycles with any of the signals between 4 megacycles and 4.9megacycles and filtering the resulting output signals to obtain tenthousand one hundred cycle separated signals between 40 megacycles and40.9999 megacycles;

(q) means for combining the signals between 40 megacycles and 40.9999megacycles with the 34.9 megacycle, the 35.9 megacycle, and the 36.9megacycle signals and filtering the resulting output signals to obtainthirty thousand one hundred cycle separated signals between 3.1megacycles and 6.1 megacycles; and

(r) means for multiplying the frequency of the signals between 3.1megacycles and 6.1 megacycles by a factor of then to obtain thirtythousand one kilocyclev separated signals between 31 megacycles and 61megacycles.

References Cited by the Examiner UNITED STATES PATENTS ROY LAKE, PrimaryExaminer.

JOHN KOMINSKI, Examiner.

